Overlay networks in general, and Internet protocol (“IP”) overlay networks in particular, are gaining popularity for providing virtual machine (“VM”) mobility over L3 networks. Virtual eXtensible Local Area Network (“VXLAN”) is a technique for providing an L2 overlay on an L3 network. In particular, VXLAN is used to address the need for overlay networks within virtualized data centers accommodating multiple tenants. In such overlay networks, native frames are encapsulated with an outer IP overlay encapsulation, as along with a VXLAN header, and UDP header. In VXLAN, each overlay is referred to as a VXLAN segment. VMs within the same VXLAN segment are within the same layer 2 domain. Each VXLAN segment is scoped through a 24-bit segment ID, referred to as a VXLAN Network Identifier (“VNI”), which allows up to 16 M VXLAN segments to coexist within a single administrative domain. The VNID scopes the inner MAC frame originated by the individual VM; therefore, overlapping MAC addresses may exist across segments without resulting in traffic cross-over. The VNID is included in an outer VXLAN header envelope in which the inner MAC frame originated by the VM is encapsulated. The term “VXLAN segment” herein may be used interchangeably with the term “VXLAN overlay network.”
A VXLAN tunnel endpoint (“VTEP”) is a hardware or software component that performs VXLAN encapsulation and decapsulation. The IP address used by a VTEP as the source address for VXLAN encapsulation is referred to as the VTEP address. The VTEP address, along with the inner source MAC addresses, may be learned by remote VTEPs. Multidestination frames in VXLAN may be carried in IP multicast packets, which use group addresses (possibly allocated per Virtual Network Identifier (“VNI”)) as destination IP addresses, or carried in IP unicast packets, which are replicated at the tunnel headend. Additional details are provided in “VXLAN: A Framework for Overlaying Virtualized Layer 2 Networks over Layer 3 Networks” (draft-mahalingam-dutt-dcops-vxlan-02) (hereinafter “VXLAN Draft”), which is hereby incorporated by reference in its entirety.